Manufacture of filaments of tungsten or molybdenum for electric incandescence lamps.



, heating to incandescence in steam and hy- UNITED STATES PATENT ANTON 'LEDERER, OI: NEAR VIENNA, AUSTRIA-HUNGARY.

MANUFACTURE or. FILA'MENTS or ruucs'rsu on MoLYnDENUM FOR ELECTRIC INC'ANDESCENGE LAMPS.

No Drawing.

Specification of Letters Patent.

Patented Aug. 26, 1913.

Application filed April 24, 1306. Serial No. 313,485.

To (1.7K whom it may concern:

' Refitknown that I, ANTON LEDERER, a subject of rhisti'ia-Hungary, residing at Nof 8;) Atzgersdorf, near Vienna, in the Province of Lower Austria and State of Austria- Ilungary, have invented new and useful Improvements in the Manufacture of Filamen ts of lungsten or Molybdenum for Electric Incandescence Lamps, of which the following is a specification.

My invention relates to a process for making pure tungsten filaments or Wires for incandescent electric lamps, whereby the disadvantages and the troublesome conditions of the known processes such as denitration,

drogen and equalizing; thejfilaments, are completely eliminated and the simple and rapid manufactureof the metal filaments is insured. K.

In order to make incandescent electric lamp filaments according to my invention, a

I certain oxygen compound of the metal,

namely tungsten dioxid, is mixed with one or more organic agglutinants, such as an ammoniacal solution of casein, a solution of isinglass, levulose or gum, and the mixture is worked up into a plastic mass, which is then pressed into the form of threads in the usual manner. The latter are. allowed to dry, and they are then subjected to dry distillation in the absenceof air. During this dry distillation the carbon contained in the organic agglutinant reacts with the oxygen of the tungsten dioxid, and the reduced particles of metal consolidate with a dense, coherent and elasticfilament. In order .to completely-eliminate the carbon of the agglutinant, I proportion thequantity of agglutinant insuch a manner that the carbon contained in it is practically chemically equivalent to the amount of oxygen in the dioxid. l Vhile Various materials may be used as an agglutinant I have found that the ammoniacal solution of casein is peculiarly well adapted to the purpose, as its binding qualities are great and usually a smaller quantity of casein may beused than in the case of any other binder. In general it is desirable that the amount of binding material used shall be as small as possible. I find that the elimination of the carbon and the proper consolidation of the particles of the reduced metal into a dense and elastic filament depend to a large extent upon the proper conditions under which the process is conducted. In order to obtain the best re- V I these conditions I obtain a dense, coherent and elastic metallic filament, which consists of practically pure tungsten metal and which only contains such small amounts of carbon, that the latter can be considered completely eliminated for practical purposes. The filaments thus obtained are then heated to incandescence in absence of air by passing through them an electric current, for the purpose of eliminating any oxid they may still contain.

It is obvious that it is very difficult in practice to so proportion the carbon of the binder to the oxygen of the tungsten dioxid that they are absolutely chemically equivalent- For this reason I prefer to add .a little excess of oxid, which excess I volatilize by the heat of the electric current. As my filaments are already practically completed after the dry distillation process, they are very good conductors of electricity. I therefore do not heat them up gradually to a very high temperature, but subject them at once to a high heat. If the proportion of carbon to the metallic oxid should be in excess, a filament consisting of metal and metal carbid is obtained. This has a much higher electrical resistance than that of a pure metal filament,and if heated to moan desc'ence, will scatter the carbon contained in it owing to electrolytical dissociation. The carbon thus eliminated from the filament deposit only the inner surface of the lamp bulb and blackens it. It is obvious, therefore, that I do not aim at producing any metallic carbids, and that it is preferable for me to use a slight excess of oxid.

The filament obtained by my process has a shining surface of metallic luster and chemical analysis proves that the filament consists of pure metal.

. \Vhat I claim as my invention is:

1.- In the process of manufacturing pure metallic filaments for incandescent electric lamps, a paste for squirting the raw filaments composed of an oxygen compound of a refractory metal and an agglutinant contungsten filaments for incandescent electric lamps, a paste for squirting the raw fila posed of tungsten dioxid and an agglutinant;

10 consisting of an ammoniacal so lution 'of casein. z

4. In the process of manufacturing pure "tungsten filaments for incandescent electric lamps, a paste for squirting the raw fila 15 ments composed of tungsten dioxi-d and a' sufficient amount of an agglutinant consisting of an ammoniacal solution of casein, so that the carbon of the agglutinant is not in xexcess of the amount chemically equivalen 20 to'the oxygen of the tungsten dioxid.-

- 5. The process of manufacturing. filaments for incandescent electric lamps, which I quantity of tungsten dioxi-d and a'suflicient amount of organic agglutinant composed of an ammoniacal solution of casein, so that the carbon contained in it is not in excess of the amount chemically equivalent to the oxygen of the dioxid, forming threads from .the plastic mass thus prepared in the usual manner, and subjecting the same to dry distillation, thereby converting the carbon of the ag'glutinant into carbon monoxid or ticles'of reduced metal into 'a dense and coherent filament. i

In testimony whereof I have signed my name to this specification in the presence'oi? two subscribing witnesses.-

, ANTON LEDERER, Witnesses:

J OHANN LUX ALvEs'ro S. Hoct'm.

consists in preparing a past Containingv dio-xid, reducing the tungsten dioxid to" metallic tungsten and consolidating the par- 

